Avoid iridium, and platinum like the plague. Go with copper core at least, at best use what is printed on the sticker. The techs who fix these engines, will be on shortly(usually),to tell of the problems iridium, and platinum has had with these engines. Also change them ASAP, the plugs should be changed every 30000 miles. After 4-5 years, if you drive like my family your well past that.

I know I didn't just hear someone say bosch and spark plugs in the same sentence on a jeep site. Yeah Jbarthol called it, some of us would be on here to say do not use bosch anything that screws into the engine. Even euro trash is going to other brands. NGK coppers are the exact OE plug, and most KJs have the part number on the emissions sticker even. Some don't like NGKs, and use Champions. The 4.7L(sister engine) uses Champions as their oe plug. The only real difference is a slightly different heat range. Iridium and platinum plugs are good plugs, in the engines that require them. Gaps have to be different than copper plugs due to a difference in performance. Our engines run best on plain old cheap copper plugs, and take 20 minutes to change, every 30k. Not a hard job.

Being you have a '02 also might want to recheck what you wrote as far as gap goes.

And it's 15lbs-ft,not 20.

Page 8I-3 of the 2002 Daimler Chrysler Liberty Service Manual states 20 ft. lbs. of torque for the 3.7L engine and 15 ft. lbs. for the 2.4L engine. It also states 0.042 in. for the spark plug gap. My local Jeep dealer's Service Dept. said 0.044 in. is the correct gap for the plugs.

Page 8I-3 of the 2002 Daimler Chrysler Liberty Service Manual states 20 ft. lbs. of torque for the 3.7L engine and 15 ft. lbs. for the 2.4L engine. It also states 0.042 in. for the spark plug gap. My local Jeep dealer's Service Dept. said 0.044 in. is the correct gap for the plugs.

And typically, there is a note, to see the emission sticker for vehicle specific info. 0.040" is spec. Also, right out of Mitchell Ondemand5, 20ft-lb torque spec, and 0.040" gap. This info is taken from the OE.

Double checked under the hood this morning and the sticker says .040, pulled them out and re-gapped them and torqued to 20 ft. lbs. as per spec. So much for listening to the service guy at the dealer. Never noticed the info was right on the sticker.